Protection against bullet spatter



Aug. 20, 1946. w. E. SWIFT, JR 2,406,047

' PROTECTION AGAINST BULLET SPAT'ITER Filed Feb. 18, 1943 3 Sheets-Sheet 1 a I 5 m ffifif LA 1 I '4 FlG.5

2a INVENTOR \l WILLARD E. SWIFT JR.

' QEWMRM ATTORNEYS Aug. 20, 1946. w. E. SWIFT, JR 2,405,047

. I PROTECTION AGAINST BULLET SPATTER Filed Feb. 18, 1943 3 Sheets-Sheet 2 FIG. l5

INVENTORI 22 WILLARD E.SWIFT JR.

F I v c. IMwfZ Z J ATTORNEYS Aug. 20, 1946.

W. E. SWIFT, JR

' FIG. 25

ATTORNEYS Patented Aug. 20, 1946 UNITED STATES PATENT OFFICE V 1 Claim.

amended The invention described herein may be manufactured and used by or for the Government for governmentalpurposes, without the payment to meof any royalty thereon.

This invention relates to the prevention of damage caused by bullet splash or spatter entering crevices and openings through the walls of armored. structures such as combat tanks and the like.

Bullet splash or spatter is the phenomenon that occurs when small arms fire strikes an armored surface. Particles of the outer shell and inner core of the bullet are thrown in all directions laterally from the point of impact. At least some of these particles skim along the surface and enter any opening in line with the surface. Moreover, on striking another surface, the spatter is again deflected in all directions, although with diminished force. Consequently, the bullet spatter may be deflected into openings and will pass through to the interior of the structure. This action occurs even if the opening follows an ir- .either case immobilizing the movable part.

The invention resides in providing various means for deflecting the spatter either at an intermediate point in its path or at the end of its path through the opening, immediately before it enters the interior of the armored structure. The various forms of deflecting means can be best selected and applied after an understanding a of the behavior of bullet spatter, and for this reason the phenomenon is discussed to some extent herein.

. The invention is basedlargely on the discovery and analysis of the distribution of the spatter. As a result of such observations, I have found that a number of deflecting surfaces introduced in the path of the spatter will progressively reduce its momentum until it loses its damaging effect. Another construction based on these observations is the provision of a concave surface presented to the path of the spatter and extending through approximately 180 degrees, so that the direction of thespatter is substantially reversed. Where such a construction becomes too expensive or is April 30, 1928 370, O. G. 757) otherwise impracticable, a float deflector may be inserted in the path or at the end thereof, secured to one of the walls of the opening and forming with this wall an acute angle facing the incident end of the opening.

The underlying theories of the invention are illustrated schematically, and som illustrative embodiments are. shown in the accompanying drawings in which:

Figures 1 to 13 inclusive are schematic illustrations of the behavior of bullet spatter under various conditions described below;

Figures 14 and 15 are detail sections of a tank turret having spatter protection for the sight opening;

Figures 16 to 20 inclusive are detail crosssections of various armored structure equipped with spatter protection devices;

Figure 21 is a detail cross section of a door structure showing a difierent form of trap for the crack;

Figure 22 is a detail section of a door or other structure presenting an opening, with spatter defleeting surfaces formed in the opening;

Figures 23 and 24 are detail sections of a gun rotor with a spatter trap beyond the clearance;

Figure 25 is a detail section of a gun rotor and housing with spatter traps in the clearance;

Figure 2 6 is a reproduction of Figure 23, illustrating the path of armor piercing fragments, and I Figure 27 illustrates a similar but shorter p and the insufficiency thereof.

Reference to these views will now be made by use of like characters which are employed to designate corresponding parts throughout.

By way of introduction it is pointed out that the spatter behaves in many respects like a fluid and follows substantially a fluid path on surfaces and in crevices, This will be observed throughout the detailed description.

Figure 1 illustrates normal incidence against a semi-hard fiat surface I. The bullet approaches along the arrow 2, and the spatter is distributed in all directions from the point of impact along the plane of the surface as indicated by the arrows 3. The bullet is a ball cartridge which does not penetrate the surface.

In Figure 2 an armor piercing projectile 4 has struck the member 5 and produced a similar pattern. The projectile has also formed a crater 6, the effect of which will presently be pointed out.

Figure 3 ,illustratesthe. impactjat anangle of about 45 degrees to the member I... The spatter again radiates from the point of impact but the distribution is not uniform. It is about 20 per cent in the acute angle and about 80 per cent in the obtuse angle. A similar effect occurs at larger angles of incidence, such as '75 degrees to Figures 5 and 6 show characteristic patterns 1 when the plate is chipped orwhen the "armor piercing core of the bullet is broken. Where this happens, the bullet spatter from the-jacket or shell-is somewhat similar to that produced by ball ammunition, skimming'along' the plate as indicated by arrows. H. However, the core fragments and particles of the plate, indicated by the numeral l2, fly off in a haphazard manner. It might be noted here'that' an armor piercing core is quite likely to shatter on striking a semi-hard surface l3 at an angleas shown in Figure 6, but would not do so with a'normal hit. '1

Figure 7 shows the effect of a bullet striking a hard, convex surface l5 at normal incidence. Whether the surface is cylindrical or spherical, the spatter is distributedin-a plane tangent to the surface at the point of impact, as indicated by the numeral l6; This is true even-if the incidence is not radial, as indicated by the numeral I1. Armor piercing ammunition on a hard surface; where the core or plate is shattered, does not follow this rule.' Softer targets are discussed below. T 1

Figure 8 shows the spatter distribution resulting from an impact of ball ammunition on a hard, concave cylindrical surface It. The spatter radiates from the point of impact as for any other hard surface, but is deflectedby the adjacent curved surface and is substantially reversed in direction if the total curvature of the surface approaches 180" degrees. Centrifugal force causes the particlesto hug'the surface of the plate. The concave surface is one of the most useful means of spatter control if it can be economically incorporated in the construction.

Figure 9 illustrates deflection of'spatter at an intercepting surface. the first plate in the manner described. A portion striking the nearby angularly disposed plate 2| again radiates from the point of impact. Due to this behavior, some of the spatter entering a jagged path will emerge at the other end of the path. The velocity is of course reduced with each impact. V

On softer surfaces, such as cast armor and soft homogeneous plate where ball ammunition produces more or lessof a crater, the spatter pattern is influenced by that crater. The spatter distribution on cast armor plate of about 300 Brinell is shown in Figure 10 and on cold rolled steel plate'ifi in Figure 11. The direction of spatter is approximately a prolongation of the wall of the crater, and'the smaller the included angle, the narrower is the pattern. Thus, there is less danger when a crater is formed, since a greater portion of the spatter is thrown away fromtheplate. I

The spatter radiates along Figures 12 and 13 show spatter from a soft convex surface 21 and from a soft concave surface 28. The direction of the spatter is not materially influenced by the shape of the surface.

Figure 14 shows the turret 30 of a tank having a sight opening 3|. In an unfavorable design, this opening would be approximately in the upward projection of the sloping front plate 32, since the spatter would be directed towards the opening. Figure 14 shows the plate 32 disposed at such an angle that its projection lies considerably above the opening 3|.

However, where a less favorable angle cannot be avoided, one or more angle irons 3 3 are secured across the front plate, as shown in Figure 15. These irons obviously deflect the spatter before it reaches the sight opening. 'If any spatter should travel beneath the first angle iron, it will be stopped by the second iron.

Figure 16 shows a door 40 closing against a wall or plate 41, leaving an angular crack 42. Reference to Figure 9' shows that a hit on the wall would spatter through the crack. A deflecting bead 43 near the entrance end of. the crack is useful on hard plate, throwing the surface spatter upward.

The treatment of. a direct hit at the entrance of the crack is shown in Figure 17 where a door 44 similarly closes against a wall or plate 45, leaving an angular crack 46. A deflector in the nature of a flat trip 41 is secured to one of the walls of the crack or a prolongation thereof, forming with this wall an acute angle facin into the direction of travel. spatter entering such a trap loses most of its velocity because of the sharp angle of deflection and is relatively harmles on leaving the trap.

' Figure 18' shows an improvement of this arrangement wherein the door is beveled oil" at 48 directly adjacent to the free edge of the strip 41'. The beveled edge deflects the spatter back into the crack in cases where the spatter origimated with sufficient energy to maintain velocity after entering the trap. Tests have shown that occasionally 1% inch stock will be blown out by direct hits. Therefore, twelve gauge stock should be used and should be carefully welded in place. The sharper the turn made by the spatter, the more energy it loses in the turn. This applies also to curved deflecting surfaces.

Figure 19 and 20 illustrate the embodiment of into the general direction of origin by bypassing or re-direction. In Figure 19 a door 50 closes against'a wall or plate 5!. A substantial space 52 is maintained between the parts, and a concave surface 53 is formed at the bottom of the space. Spatter from adirect hit at the entrance to the space is reversed or re-directed by the concave surface as shown by the arrows. v

In Figure 20 two parts 54 and 55 are spaced to form a slit 56. A concave surface 5'! formed on one or both of the parts adjacent to the slit throws the spatter across the slit. When the material is Where close tolerance is not required, the construction shown in Figure 22 may be used. The part 62 overlaps the part 63 and is formed with a rather large concavity 64. Opposite this, the part 53 is formed with a smaller concavity 65. The effect of a hit at the entrance end of the space is illustrated by the arrows.

This construction is efiective for ball ammunition but passes some fragments produced by armor piercing ammunition. It should therefore not be used Without additional protection.

A practicable treatment of a curved path is shown in Figure 23, between a gun rotor H3 and its housing I l. The spatter travels around the curve and is held very close to it by centrifugal force. A simple trap 72 i secured to the housing and forming an acute angle facing into the direction of travel, serves to catch the spatter.

Closely machined tolerances are often used to eliminate spatter. These result in slow and expensive production and immobilization of the rotor from dust, dirt, rust and burring by small arms fire. An efiective trap permits larger tolerances.

An alternative construction is shown in Figure 24 where the trap is in the form of an involute 73 having an angularly disposed end T4. The spatter entering the trap is forced into a circular or whirling movement which reduces the velocity.

Another arrangement for a rotor is shown in Figure 25. A number of strip are secured at intervals to the housing, each forming an acute angle facing into the direction of fire. This arrangement is very eiTective in trapping all the spatter.

Figure 26 is a reproduction of Figure 23 to show the effect of armor piercing bullet fragments. The fragments rebound from the armor in paths designated by the arrows at. Little or no spatter escapes. This view illustrates the fact that adequate protection may be obtained if sufficient curved surface is available. Otherwise some of the particles will escape, as illustrated in Figure 27. Here the housing Tl provides a shorter curved path than in Figure 26. At the end of this path the fragments still retain suficient velocity to escape with appreciable momentum, as shown by the arrows.

The foregoing illustrations and descriptions show that effective spatter traps can be built for practically all structures. Although the traps shown for gun rotor are not altogether effective against fragments from small arms armor piercing ammuntion on direct hits, they undoubtedly have considerable value on les direct hits.

The efiectiveness of the trapping within a rotor housing depends on the dimension of the clearance and the length of the curved path. The trapping is more elfective in a longer path. Small clearances are likely to result in locking of the rotor, due to the wedging of particles therein and burring of the surfaces, which has the same effeet. A clearance of inch is not sufiicient to prevent locking in this manner, and a wider clearanoe is recommended for use in connection with a trap.

Variou embodiments of the invention have been illustrated and described. It is to be noted that the particular construction to be used should be selected in view of the nature of the apparatus Where it is to be installed and in the light of principles herein discussed. Adaptation of the trap structure, indicated by these principles, may also be necessary.

What I claim is:

A door joint comprising, in combination, a hatch member having a hatch way with an arcuate shaped recess on the inner side thereof, a hatch cover having an extending marginal portion for overlapping the marginal portion of the hatch in said hatch member when it is engaged therewith, the underside of said projecting overlapping portion receding into the arcuate contour of a recess in the outer side of said hatch cover, said arcuate shaped recess having the bottom side theerof in substantially the same horizontal plane with the bottom portion of the recess in the inner marginal portion of said hatch member.

WILLARD E. SWIFT, JR. 

